Crucial questions regarding the mineralizing processes involved in the formation of disseminated gold mineralization remain unresolved, which complicates our understanding of metal precipitation processes in these systems and impedes effective exploration. This study integrates petrographic and geochemical analyses of chlorite within barren and ore-bearing marble, granite, and granofels units from the Guocheng gold deposit in Jiaodong, China. The petrographic analysis of these samples indicates that ripidolite is the primary chlorite phase within altered wall rocks, replacing biotite, hornblende, and plagioclase via dissolution-crystallization. In contrast, ore-associated chlorite is dominated by brunsvigite and pyrochlore, forming by dissolution-migration-crystallization. The mineral chemistry of this chlorite indicates that ore-related chlorite has lower Fe²⁺/(Fe²⁺ + Mg²⁺) ratios and higher Fe³⁺ concentrations than chlorite within altered wall rock areas. This indicates relatively lower amounts of ion substitution and suggests relatively higher oxygen fugacity conditions in the ore-forming environment. Furthermore, chlorite formed during mineralization exhibits elevated Mn but decreased Ti, Ni, Co, and Rb concentrations compared to altered wall rock-hosted chlorite, coupled with lower Rb/Sr ratios. These geochemical signatures indicate that the low-salinity H₂O-CO₂-NaCl ± CH₄ ore-forming fluids mobilized only limited quantities of these elements during transport. These data indicate that ore-forming fluids interacted with ferreous minerals in the high-oxygen-fugacity wall rocks under high water-rock ratio condition, which elevated the oxygen fugacity of this part of the system by the precipitation of Fe-rich carbonates and magnetite. The resultant decrease in Au(HS)₂⁻ complex stability enabled efficient gold precipitation. These data also provide insights into variations in chlorite Fe²⁺/(Fe²⁺ + Mg²⁺) and Rb/Sr ratios, as well as concentrations of Mn, Ti, Ni, Co, and Rb, and ion exchange intensities, further discriminating mineralized and barren regions in the same host rocks within the Guocheng gold deposit. The findings enhance understanding of hydrothermal alteration linked to gold precipitation and highlight chlorite’s potential as a fertility discriminator in the Guocheng gold deposit.